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This article in SSSAJ

  1. Vol. 28 No. 4, p. 511-517
    Received: Nov 18, 1963



A Study of Isotopic Dilution as a Method for Relating Phosphorus Retention to Availability of Phosphorus in Widely Different Soils1

  1. Dale E. Baker2



Six soils which were considered different with respect to release and retention of P were limed and allowed to equilibrate with a constant amount of P32 and 25, 100, and 400 ppm. of P31 by alternate wetting and drying 4 times prior to seeding Turghi millet and Tokyo buckwheat. The objective was to relate P retention characteristics to “availability of P” in different soils. “Active solid phase P” as determined by isotopic dilution was found to be an index of the amount of “available P” contained in a soil. A constant proportion of the active solid phase P was not in solution or removed from all soils by any of the extracting reagents. The percent active solid phase P removed by all extractants was affected by the rates of added P. From the results it was concluded that the percent active solid phase P removed by Bray's No. 1 extractant from each soil type was an index of its retention characteristics, if the native active solid phase P was in equilibrium with the added P32.

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